The present disclosure is related to the field of access networks, particularly to a method for monitoring upstream burst performance in a point to multi-point (P2MP) access network.
Presently, there are access networks that broadcast downstream traffic using Time Division Multiple Access (TDMA) and use bandwidth sharing for upstream traffic, e.g. Broadband Passive Optical Network (BPON), Ethernet Passive Optical Network (EPON), and Gigabit Passive Optical Network (GPON). These networks have a point-to-point structure and comprise a Head End (HE), a distribution network, a Terminal End (TE), and an End User Device, where the HE may be an Optical Line Terminal (OLT), the TE may be an Optical Network Terminal (ONT), and the End User Device may be a Personal Computer (PC). From the HE to the TE is the downstream direction, and from the TE to the HE is the upstream direction. Referring to the network topology shown in FIG. 1, the HE sends downstream traffic to the TE and the End User Device via a splitter/coupler in the distribution network using a Time Division Multiplex (TDM) broadcast, while the TE sends upstream traffic to the HE using TDMA. Depending on the specific situation, the distribution network may not be limited to the single-level embodiment illustrated in FIG. 1.
One of the key technologies in the network is the TDMA technology that is used for upstream bandwidth sharing, the working principle of which is illustrated in FIG. 2. Generally, the HE first measures the distance from the HE to each TE, makes the logical distance to each TE the same by compensating for each TE's time delay, and then uniformly manages and allocates upstream bandwidth using Dynamic Bandwidth Attribution (DBA) technology. Each TE sends its upstream data burst in the timeslot authorized by the HE, so that upstream collisions are effectively avoided. In FIG. 2, the numbers 1, 2, and 3 in the boxes represent data belonging to the TEs 1, 2, and 3 respectively, which includes downstream data from the HE to the TE as well as upstream data from the TE to the HE. When the HE sends downstream data 1, 3, 2, 1, 3, and 1 through the distribution network (not shown in FIG. 2) to the TEs, TE1 picks out its own data, 1, from the received downstream data and discards the other data. Similarly, TE2 and TE3 pick out their own data, 2 and 3 respectively, and discard the other data. For upstream data, the TEs send their data to the HE according to the timeslots authorized by the HE. For example, TE1 sends data 1 according to the HE's authorization, TE2 sends data 2 according to the HE's authorization, and TE3 sends data 3 according to the HE's authorization. Because the data sent from the TEs are sent in the timeslots authorized by the HE, the upstream data from TE1, TE2, and TE3 arrives in order at the HE, collision of upstream data is avoided, and the HE correctly receives the upstream data.
However, there are risks for a network working under this principle. For example, one of the TEs may have an uncontrollable exception, which may be due to the TE's hardware and/or software failing or hackers maliciously operating the TE. The TE with the exception may not send upstream data according to the HE's authorization, may not send any upstream data, may continuously send upstream data bursts, or may send upstream data bursts in unauthorized timeslots. Here, the TE with the exception is called a Rogue TE. When the rogue TE does not send upstream data bursts, some of the upstream bandwidth is wasted, but the normal operation of the entire network is unaffected. When the rogue TE continuously sends upstream data bursts, it causes upstream data burst collisions in the HE receiver, such that the data signals overlap. When this occurs, the HE will not be able to receive the upstream data from the TEs, and the whole network's upstream channel jams.
Referring to FIG. 3, when TE3 is controlled by a hacker or has a hardware or software failure, it does not send upstream data in the designated timeslots but continuously sends upstream data. Data sent by TE3 in the unauthorized timeslots collides with data sent from the other TEs and prevents the HE from correctly receiving upstream data from the TEs. The question marks in FIG. 3 represent unrecoverable data signals caused by upstream data burst collisions.